1. Field of the Invention
This invention relates to heating the diesel fuel in a diesel powered vehicle. More specifically, the invention relates to an apparatus that simultaneously heats the diesel fuel being pumped to the engine as well as the excess fuel recirculating to the fuel tank by liquid/liquid heat exchange with hot crankcase oil.
2. Description of the Prior Art
The basic concept of heating the fuel/air mixture entering an internal combustion engine is generally known in the art. The reason or incentive for heating a gasoline and air mixture before combustion is usually related to increased efficiency and economy associated with improved vaporization of the gasoline droplets. Thus, it is generally known to heat the fuel/air mixture either before, during or after passing through the carburetor. A variety of types of heating devices have historically been suggested and employed including various electrical heaters, equipment to direct combustion exhaust gases through heat exchangers in contact with incoming fuel/air mixture, and equipment that uses hot crankcase oil in a manner similar to the exhaust gases. For example, in U.S. Pat. No. 2,125,216, the fuel/air mixture exiting a carburetor is heated with hot crankcase oil before entering the intake manifold. U.S. Pat. No. 3,016,890 discloses a method of circulating hot oil in the air filter to heat the air entering the carburetor. In U.S. Pat. Nos. 3,916,859 and 4,169,442, hot oil is circulated through a hollow stem of the carburetor throttle valve to prevent icing in the carburetor.
In the case of a diesel engine, it is generally known and an accepted practice to heat either the fuel line, engine or both to assist cold weather starting. This is commonly achieved by plugging in an electric heater to an external electrical source prior to starting. This heating is usually envisioned as being necessary to prevent or inhibit the paraffinic components of the diesel fuel from depositing in the fuel line and injectors, thus clogging the fuel system. However, there is another incentive to heating diesel fuel which has been generally ignored; ie., a controlled warmed source of diesel fuel will allow the engine to perform more efficiently. Thus, a need exists for an inexpensive yet reliable method and apparatus to supply uniformly heated diesel fuel being injected into a diesel engine.